UV Image Editor Display "Repeat Image" Zoom Problem
Just closing the loop on this one. Apparently, this is considered "expected behavior" for the moment. There is a .25 second window during which the graphics are allowed to be drawn. Past that time, rendering of the image stops to avoid bottlenecking the system or causing it to bog down.

While that is surely valid, it means that using small textures repeated lots of times and UV-mapping it over a large area (such as tiles on a huge roof, for example) is not possible.